This invention relates to the construction of automobile seats, and is directed particularly to the manner of attachment of a headrest to the frame of an automobile seat.
The headrest on an automobile seat is often made adjustable as to height. One common way in which the headrest is mounted on the seat in a way that permits height adjustment is for the headrest to be provided with two downwardly extending pegs, and the pegs engage sockets secured into the frame of the seat. Detent means are usually provided which interact between the pegs and the sockets, whereby the headrest may be set, by the occupant of the vehicle, at one of a number of pre-set heights.
The socket in which the peg is received comprises a metal tube. A plastic liner may be provided in the tube, to act as a bearing material for the peg. In the conventional system, the tube is welded to a bracket, and the bracket is welded to a frame piece of the seat. This manner of attachment, though secure enough (because it has to be secure by regulation), unfortunately is expensive as to the labour time and the materials needed to make it that secure. Any securement system that involves welding tends to be labour-intensive and therefore expensive, besides being difficult to inspect and test. A welded system generally has to be over-engineered.
Also, welding does not lead to high accuracy. The need for accuracy of placement of the headrest on the seat is not high, although the accuracy of the spacing of the pegs and their sockets cannot be too far out; the conventional welded-on system is just about at the limit for accuracy for welding, which means that, when welding is used as the basis of the attachment method, skilled care has to be taken, which in turn does nothing to ease the cost problem.
The invention is aimed at providing a manner of securing a headrest support tube into a seat frame, in a manner that eases some of the compromises that have had to be resorted to in the conventional systems.
Typically, the operations carried out in a conventional seat manufactory include welding, bending of frame pieces, securing components together, and assembly, all of which tend to have a higher labour content. It is an aim of the headrest support system as described herein, to minimise the labour content of the task of attaching the support tubes to the seat frame piece.
Support tubes for headrests are conventionally attached to the seat frame piece by welding a bracket onto the frame piece, and then welding the tube to the bracket. Sometimes, the tube is pressed into holes in the welded-on bracket; but welding is nearly always resorted to, to assure that the tube remains in position on the bracket. Of course, the tubes can be attached securely enough, but the conventional costs of ensuring that security are high.
The invention lies in the manner of attaching the headrest-support-tube. First, the headrest-support-tube is provided with a first ring, in which the metal of the headrest-support-tube is expanded radially outwards. The headrest-support-tube is assembled into a hole in the web of the seat-frame-piece, with the first ring abutting against the web.
The frame-piece, with the headrest-support-tube resting therein, is placed in the die of a punch and die set, with the first ring in the die. The punch then is brought down over the other end of the headrest-support-tube, and a second ring is formed on the other side of the web. When the punch is withdrawn, the web lies gripped between the two rings. Usually, another headrest-support-tube is inserted into the frame-piece, in a similar manner. Then, the seat-frame piece is assembled into a seat, and finally the pegs of the headrest are inserted into the headrest-support-tubes.
As mentioned, headrest-support tubes are attached to the seat-frame-piece by welding. Sometimes, designers have specified intermediate brackets, rather than just welding the tube to the frame piece.
Techniques for mounting a tube into a through-hole in a piece of sheet metal are commonplace, per se. The broad range of options available include bulk-head fittings generally. Such fittings have included cases where a first bead is provided on the tube on one side of the sheet, then a second bead is swaged into the tube after the tube has been inserted into the through-hole. The technique is commonly known as lock-beading.
In cases where bulk-head fittings are being designed, a common requirement is that the fitting be air- or liquid-tight. It is recognised that the lock-beading technique is not suitable for such cases. It is recognised that lock-beading is highly suitable for cases where mechanical integrity is paramount, rather than sealing. It is also recognised that lock-beading is highly suitable for cases where access to the beads is only to be had from an axial direction, such as a case where flat-access to the through-hole is denied because the through-hole is surrounded by raised flanges.